1. Field of the Invention
The present invention relates to an apparatus for cooling a laser-type weld line detecting unit of an automatic welding machine such as an industrial welding robot provided with a laser welding torch. More particularly, the present invention relates to an air-cooling apparatus for cooling a laser-type weld line detecting unit by the flow of cooling air when the detecting unit is provided, therein, with a weld line detecting assembly and a built-in rotating mechanism capable of detecting both curved and linear weld lines along which the welding torch of an automatic welding machine, especially of an industrial welding robot, welds a workpiece. The welding torch welds the workpiece by an electric arc discharged therefrom toward desired welding lines on the workpiece.
2. Description of the Related Art
When an arc welding process, using the automatic welding machine such as an industrial welding robot, is carried out, the welding torch mounted on the welding machine is moved to pass through a desired curved or linear weld line in a workpiece to thereby apply arc welding to the weld line of the workpiece. During the arc welding of the automatic welding machine, the desired weld line of the workpiece is beforehand detected by a weld-line detecting device held by the automatic welding machine. Namely, the detecting device generally includes a laser-type weld-line detecting assembly having a laser emitter to emit a detection-purpose laser beam and to scan a programmed welding area on the workpiece by the detection-purpose laser beam, and a line CCD receiver receiving the laser beam reflecting from the area of the workpiece to detect the desired weld line. The line CCD measures a distance between the line CCD per se and the weld line, and also detects the shape of a weld area of the workpiece. The measured and detected data from the line CCD of the weld-line detecting device is used to control and adjust the path of the movement of the welding torch and the spacing between the end of the welding torch and the desired weld line in the workpiece to thereby perform accurate arc welding on the workpiece.
At this stage, when the desired weld line of any workpiece is relatively long containing therein a curved weld line portion, the laser-type weld-line detecting device is constructed so as to accommodate a rotating mechanism therein so that the laser emitter of the device is permitted to emit the detection laser, and to scan the curved weld line on the workpiece. When the laser-type weld-line detecting device accommodating therein the rotating mechanism is mounted on the automatic welding machine such as an industrial welding robot provided with a welding torch, the weld-line detecting device is disposed at a position adjacent to the welding torch mounted on the automatic welding machine. Therefore, when the laser-type weld-line detecting device is continuously used to detect a desired weld line in response to a continuous welding operation of the automatic welding machine, the detecting device is continuously and directly subjected to a welding heat generated by and transmitting from the welded portion of the workpiece. Further, the laser emitter, consisting of a semiconductor laser source, generates heat during the detecting operation. Thus, the detecting device is placed in a thermally critical condition if it is not suitably cooled. When the detecting device is heated, the accuracy in the detecting operation thereof is reduced by the heat and the operating life of the laser-type weld-line detecting device is also reduced. Namely, the laser-type weld-line detecting device is apt to be damaged by heat.
In order to prevent damage to the laser-type weld-line detecting device, two different corrective methods have been used, one being a method of predetermining the limit of continuous operation of the laser-type weld-line detecting device so as to prevent reduction in the detecting accuracy and in the operating life of the device, and the other being a method of applying liquid cooling to the head portion of the laser-type weld-line detecting device.
Nevertheless, the former method is defective in that the automatic welding machine cannot work at a high operation efficiency. Particularly, while the automatic welding machine is operated, the atmospheric temperature is gradually increased in response to an advance of the arc-welding of a workpiece, and accordingly, the laser-type weld-line detecting device must often be stopped in its operation resulting in a reduction in the operation efficiency of the automatic welding machine.
The latter method of employing a cooling liquid requires incorporation of a hermetic seal means into the detecting device for preventing the cooling liquid from directly contacting the laser emitter and the line CCD unit of the laser-type weld-line detecting device. Further, when the liquid cooling means is broken, the laser-type detecting device may be easily damaged.
Furthermore, when the liquid cooling method is employed, frequent maintenance of the laser-type detecting device is required from the viewpoint of checking the adequacy of hermetic seal to thereby prevent the cooling liquid from entering the detecting device, and accordingly, the operating efficiency of the automatic welding machine is lowered.